-- codifies existing practice in common asynchronous DCE that
use the AT command set. It identifies the protocol elements
procedures, and behaviors that were found to be held in common
among a large portion of DCE manufacturers;

-- defines a format for extension of the AT command set in an
orderly fashion. It reserves the "+" command prefix to be used by
other standardized extensions;

-- provides a set of standardized extensions, based on the
extended "+" command format.